create table users (
  "user_id" serial not null primary key,
  "username" varchar not null unique ,
  "password" varchar not null,
  "email" varchar not null unique,
  "full_name" varchar,
  "birth_date" date ,
  "sex" varchar ,
  "bio" varchar ,
  "avatar" varchar
);

create table lobby (
  "lobby_id" serial not null primary key ,
  "creator" int not null references users (user_id),
  "title" varchar not null unique,
  "type" varchar not null,
  "logo" varchar,
  "history" text
);

create table chat_members (
  "chat_member" int not null references users(user_id),
  "policy" varchar not null,
  "lobby" int not null references lobby(lobby_id),
  primary key (chat_member, lobby)
);

create table messages (
  "sender" int not null references chat_members(chat_member),
  "date_time" timestamp not null,
  "message" varchar not null,
  "attachment" varchar
);